Calibrator for lead-computing sights



July 26, 1949., w. McK. HORTON CALIBRATOR FOR LEAD-COMPUTING SIGHTS Filed Sept. 13, 1946 Q ON INVENTOR. WILLIAM McK/NLEY HORTON ATTORNEY Patented July 26, 1949 UNITED CALIBRATOR FOR LEAD-COMPUTING SIGHTS William McKinley Horton, Camden, N. J.

Application September 13, 1946, Serial No. 696,974

(Granted under the act of March S, 1883, as amended April 30, 1928; 370 0. G. 157) 7 Claims.

This invention relates to machine-gun sights, and more specifically to devices for calibrating the aiming corrections in azimuth and elevation that are introduced by a lead-computing sight when following a moving target.

An object of the invention is to facilitate the checking and calibrating of lead angles introduced by a gyroscopic lead-computing sight into the aiming of a machine gun to compensate for speed and direction of travel of a moving target, through the use of a device that is inexpensive to make, easy to use, ac'cmate, and dependable.

Further objects and advantages of this invention, as well as its construction, arrangement and operation, will be apparent from the following description and claims in connection with the accompanying drawing, in which Fig. 1 is a side elevation (partly in section) of a machine-gun barrel fitted with a lead-computing sight and with one form of the calibrating device that is the subject oi this invention; and

Fig. 2 is a sectional view taken along the line 2--2 of Fi 1.

211; is pertinent to review the operation of a lead-computing sight as applied to the aiming of a machine gun, :in order to establish the great utility of the present invention. Machine-gun harrel :1 a is supported by a structure that permits thesaid barrel to be tilted up or down and turned to left or right at will, so that the said barrel can :be aimed at a stationary or moving target. the said sup orting structure is not concerned in this description and hence vis omitted irom the drawing. Li -sad--cornputirig mechanism 12 :is attached to gun barrel It and is adapted to carry a sight M through which the machine-gun operatorviews the target along the line of sight 28.

heail-computer 422 usually embodies :two directionesensitive mechanisms, such :as igyrosc'opes, one of which is responsive to each component of rotational movement of barrel I 0, i. e., in azimuth or in elevation. Such rotational zmovenient influences the respective gyroscope to precess, or deviate from its original orientation, amount that is a measure :of the rate,- or angulargspeed, of such rotational movement. Through appropriate mechanism that takes into account the ballistic characteristics rot the pro- .iiectiles fired from :gun barrel Hi, the .said tendency ts "process is expressed as .a deflection :oi sight is with respect to gun barrel J0 throughlan angle the magnitude of which is substantially rproportional ito theeaiorementioned angfilarrspeed of rotational movementpf gunebarrel Ill and the direction of which is substantially i'pposlte 55 Bracket $4 is m thereto. The object of so doing is to advance the gun barrel in ahead of the line of sight 28 in the direction of movement, so that projectiles tired from said gun barrel will intersect the anticipated path of the target simultaneously with the anticipated arrival of said target at such point of intersection.

The present invention provides simple apparatus for testing whether the above described automatic mechanism for causing the gun barrel to lead the line :of sight is introducing the correct angle of lead. The lead-computer could be calibrated by mounting said -lead-computer on a fixture that can be rotated at predetermined speed in azimuth or in elevation, concurrently observing the amount of deflection that said lead-computing mechanism introduces into the orientation of sight 14. Such means, however, is not practicable for use the iield or aboard ship. In the past, when it has :been necessary to check or calibrate said lead-computing sight, it has been the practice to lay out a series of aiming points, for example by marking at appropriate places onthe :ships structure, and thereafter to setup a procedure for viewing said aiming points successively through :sight :14 and recording the time intervals that elapse between the transit of line of sight 28 across successive aiming points, simultaneously recording the corresponding readings of :azimuth or elevation obtained from protractor scales that are associated with the supporting structure ior =g-un barrel 150. The result- "ing data were plotted 'in graphic form or tabudated, :and analysis or the said data was made :to determine the relationship existing between the rate of angular movement of the said gun barrel and the amount of deflection :of line of sight 28. Gbv iously the foregoing procedure is laborious, cumbersome, time consuming, andidifilcult of accomnlishment with sufficient accuracy, since .sev- .enal factions must be recorded simultaneously and must later he interpreted.

In contrast, the device disclosed in this specification greatly simplifies the procedure and in- :creases the accuracy of results. Tube i8 ,is adapted to fit *within gun :barrel to, said tube having an internaltaiper 10 at one end and being split longitudinally tor a portion of its length adjacentfto :saidsend. "Rod 18 carries a complementary external :taper :seating in taper 10 .of rtube 1| .6, and is .adaptedito exert a wedging action ion said tube by ztakl-ng up :on nut 22, thereby flocking tube a! 6 in "position within :gun barrel .IIO. rigidly to tube .45 and 'it lags the direction of the gun barrel.

carries at its upper end a scale 26, which is mounted rotatably on said bracket so that said scale can be disposed horizontally or vertically for checking respectively azimuth or elevation corrections introduced into line of sight 28 by lead-computer I2., Other forms of the device can be used, as for-example in director-control systems where lead-computer I2 is not attached to gun barrel H], but is mounted separately and di-.

rects the aiming of said gun barrel through electrical or other means of control. In such case scale 26 is supported by a bracket that is attached to a convenient point on the movable structure that includes lead-computer I2, so that the said scale is in definite physical relationship to said lead-computer. H

In use, the device is assembled to a gun barrel ID by application of the tube 16 and rod l8, or to a director by bracket, as hereinbefore described. Scale 26 is placed horizontally or vertically, its position being such as to indicate zero deviation in azimuth or elevation, respectively, of the line of sight 28, when the machine gun or director is at rest.

The operation of the device is as follows: The

line of sight being directed at any point on scale 28 when the gun barrel is motionless, some other point on the scale is selected by the operator to represent a moving target. The operator then proceeds to move the gun barrel in the direction pposite that of the selected point (target). At once the lead-computer moves the sight so that (Inreal operation this causes the gun to deliver bullets that are ahead of the line of sight but will later meet the real target in flight.) gtor seesthe-target in the line of sight, he con- :tinues to move the gun barrel and so long as When the opera- -he moves it with-constant angular velocity the line of sight remains fixed on the selected point (target) of the scale. While such constant-speed motion is being effected, an observer notes the length of time required to traverse a predetermined angular displacement in azimuth or elevation as the case may be. This observation-involves only the manipulation of a stop-watch, starting such stop-watch when a selected protractor reading is indicated and stopping said stop-watch when another selected protractor reading is indicated. Since the selected index on scale 26, to which said index the line of sight 28 was directed, is a measure of theamount of deviation introduced into said line of sight by lead-computer l2, and since the speed of angular movement of gun barrel in is determined readily.

from indicated stop-watch time as related to the angular displacement traversed in such time, reference can be had to a prepared table for verifying the correctness of such amount of deviation of line of sight.

Operation of the device can be further simpli- 'fied by providing scale 26 with indicia, each of which is designated by a figure representing a length of time, the location of each indicium being such as to determine an angle of deflection of line of sight 28 that ought to correspond (according to relationships previously derived either mathematically or empirically) to a rotational speed of gun barrel In such that a predetermined "standard angular displacement of the said gun barrel will be traversed in said length of time. For example, a standard angular displacement of 30 may be established, and indicia can be placed on scale'28 at locations each of which corresponds to an angle through which the line of sight ought to be deflected when the gun is moving at one of several speeds that are such as to cause said gun to traverse in, for example, 5, 10, 15, 20, 25, or 30 seconds, the said indicia then being marked 5, 10, 15, 20, 25, and 30 respectively. In that event, it becomes necessary only to select a specific figure on scale 26, for example 10, then to manipulate the gun to keep line of sight 28 directed at the selected figure, and lastly to determine by means of theaforementioned stop-Watch whether exactly 10 seconds are required to traverse 30 while so doing.

In any event, whether such calibration is employed or a prepared table is employed, the result of the test indicates that the lead-computer is providing either the correct, or excessive, or insufiicient, deviation in the line of sight 28, and if adjustment is necessary it can be effected and the test can be repeated. A test run for one such check can be conducted easily in a minute or so after the device is assembled to the movin structure containing the lead-computer.

Scale 26 referred to hereinbefore need not be a conventional scale with a series of markings incorporated thereon, unless so desired for convenience in use, but can be merely any object that scope of the invention.

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor;

I claim:

1. A method of testing the accuracy of direction-sensitive, lead-computing gun sight mechanism, said method comprising measuring the time during which the gun moves through a predetermined angle while maintaining the angle between the gun sight and the gun barrel fixed.

2. A method of testing the accuracy of direction-sensitive, lead-computing gun sight mechanism, said .method comprising measuring the angle over which the gun moves during a predetermined time while maintaining the angle between the gun sight and the gun barrel fixed.

3. A method of testing the accuracy of direction-sensitive, lead-computing gun sight mechanism, said method comprising bringing the sight into line with an index attached to the gun and moving the gun so that the sight stays in line with the index and measuring the angular velocity of the gun.

4. A lead-computing sight calibrator for a gun comprising atube adapted to be mounted in the barrel of such gun, means to secure said tube in such barrel, a bracket secured to said tube, and a scale mounted rotatably on said bracket.

5. A lead-computing sight calibrator for a gun comprising a tube adapted to be mounted in the barrel of such gun, a rod carried in said tube and adapted to secure said tube in such barrel, a bracket secured to said'tube, and a scale mounted rotatably on said bracket and adapted to be positioned in the line of sight of such gun.

I 6. In a gun having a lead-computing sight, a

sight calibrator comprising a tube adapted to be mounted in the barrel of such gun, a rod carried in said tube and adapted to secure said tube in such barrel, a bracket afllxed to said tube extending substantially normal to the axis of said tube, and a linear scale mounted rotatably on said bracket, said scale being adapted to lie in the line of sight of such gun.

'7. In a gun having a lead-computing sight, a sight calibrator comprising a tube having an internal taper at one end and being split longitudinally for a portion of its length adjacent to said end, said tube being adapted to be mounted in the barrel of such gun, a rod having a complementary external taper carried in said tube, said rod wedging said tube against such barrel, a bracket aflixed 6 to the other end of said tube, said bracket extending substantially normal to the axis of said tube, and a linear scale mounted rotatably on the end of said bracket distal said tube, said scale being McKINLEY HORTON.

REFERENCES CITED The following references are of record in the 5 positioned in the line of sight of such gun.

WILLIAM file of this patent:

STATES PATENTS Number Name Date 1,994,177 Nolan Mar. 12, 1935 15 2,386,420 Bailey et a1 Oct. 9, 1945 

